This invention relates to a pump for a diesel engine. More specifically, the invention relates to a dual solenoid distributor pump having two electrically responsive solenoids and a mechanical distribution valve.
Fuel delivery systems for diesel engines can be classified into three broad categories. The first category utilizes distributor pumps having a separate fuel supply line for each injector. The second category of fuel delivery system utilizes a constant pressure source in conjunction with a common rail or manifold which communicates the supply pressure to a plurality of diesel fuel injectors. In this second type of the fuel supply system, the injectors are usually of the type having a pressure intensifier. The third category utilizes what is known as a unit injector which incorporates within the injector a pumping element and the control valve.
The first category of systems does not provide sufficient injection timing control as a function of both engine speed and load. If engine timing is mechanically or hydraulically controlled, this type of system is often inflexible and does not display cycle-to-cycle or cylinder-to-cylinder adaptability for controlling the quantity of fuel injected and its related timing. In addition, high injection pressures such as pressures in the vicinity of 10,000 to 14,000 psi are limited mainly by the strength of the long lines between the pump mechanisms and the injectors. In addition, these types of fuel delivery systems falling within the first category display line cavitation and secondary injections and exhibit a relatively slow termination of injection of fuel into the respective cylinders. Secondary injection and slow termination are primarily a result of poor control of the line dynamics.
The second type of system is amenable to electrically controlling both the injected quantity of fuel and the timing of injection. In addition, the constant pressure--common rail system is capable of delivering relatively high injection pressures. However, this type of system is often extremely expensive and is of a relatively bulky size. The expense and size of the system may be attributable to the fact that the constant pressure source utilizes a pressure regulating device in addition to a number of fuel accumulators, as well as using a 3-way valve which is often required to operate against the high pressure supply. A disadvantage of these systems is high leakage caused by the constant high pressure which is transmitted to each of the fuel injectors.
The unit injector fuel systems provide all of the fuel controls in a single package. However, a significant disadvantage of the unit injector is that the diesel engine must be modified or supplied with separate crankshaft, rocker arms and followers to drive the pumping element of the unit injector. This forecloses the use of the unit injector on standard diesel engines absent a significant redesign or modification of the engine. In addition, since each unit injector must be provided with a control valve the packaging or placement of the injector into the engine or cylinder head is more difficult when compared to the placement and packaging of smaller pressure activated injector valves as utilized by the present invention.
To meet future diesel fuel injection system operating requirements as to fuel economy and emissions control requires high performance. These performance requirements include: (a) high injection pressure of 15,000 psi or more; (b) that the injection system be capable of independent timing and metering control as a function of engine speed and load; (c) that the fuel system be able of controlling its cooperating fuel injector to display injection rate control and display an abrupt termination of fuel injection; (d) that the fuel injection system offer cycle-to-cycle and cylinder-to-cylinder adaptive control; (e) that the fuel injection system can be adapted to standard diesel engines requiring minimum engine change; (f) that the fuel injection system be of low cost and (g) that the fuel injection system display low power input, minimum power drain and low heat buildup.
The above requirements of a diesel fuel injection system are broadly met by the present invention which broadly includes a dual solenoid distributor pump that is electronically controlled, the output of which is communicated to a number of fuel injectors having an intensifier piston therein. The timing and quantitive fuel metered to each injector is controlled both on a cycle-to-cycle and cylinder-to-cylinder basis using microprocessor technology by adjusting the electrical signals to the two solenoids located within the dual solenoid distributor pump. One of the solenoid valves sequentially controls the premetering or metering function for all the injectors while the other solenoid valve sequentially controls the injector timing for each of the injectors.
An advantage of the present invention is that it may be configured to be packaged and adapated to all sizes of diesel engines with virtually no engine modification. The system utilizes a relatively inexpensive pump in combination with an injector which has a metering chamber. The fuel injection system provides the following advantages: (1) fuel metering is performed at the injector; (2) the injector is provided with a secondary dump port to abruptly end fuel injection; and (3) by utilizing an injector having an intensifier piston therein high pressure lines connected to the pump and injector are eliminated, each injector requires only a single bi-directional injection line and a single low pressure line for fuel metering.
The injector includes an intensifying piston which receives a pressure pulse as a result of the controlled excitation of the timing solenoid valve. The combined features of the distributor pump and injector result in the delivery of fluid at high injection pressures (10,000 to 25,000 psi).
The injector is also provided with a primary dump port and a laminar flow restrictor which functions to depressurize the injection line linking the distributor pump to the intensifier piston, thus preventing line cavitation and secondary fuel injection. In addition, the present invention displays the advantageous feature of constant fuel flow to each injector. This results from incorporating within the distributor pump a positive displacement pump. By utilizing only two valves to control both engine timing and fuel metering, the number of control and timing valves which are found in the prior art are minimized. In addition, by incorporating the control and timing features into the dual solenoid distributor pump permits the relocation of this timing and metering controller away from the limited space near the engine or cylinder head area.
According to the specific embodiments illustrated in the drawings of this application and discussed in detail below, the present invention comprises:
A distributor pump having metering and injection modes of operation and adapted to receive electric control signals from a controller and further adapted to receive fluid from a fluid reservoir for supplying pressurized fluid. The distributor pump comprises a housing having a return port that is adapted to be connected to the reservoir, an input port that is adapted to receive fluid from the reservoir and further having a plurality of output ports. The pump further includes a first pressure source means for supplying pressurized fluid at a determinable first pressure level and timing valve means for diverting the output of the first pressure source means to a distributor valve means during the injection mode of operation and for diverting the output of the first pressure source means to the return port during the metering mode of operation. The timing valve means being adapted to receive electrical signals in timed relationship to the combustion process within the engine. The pump further includes metering valve means connected between the distributor valve means and the return port for controlling the duration of fluid flow from said distributor valve means to the return port in correspondence with the combustion process within the engine and wherein the metering valve means is adapted to receive electrical signals in timed sequence to the combustion process within the engine; and distributor valve means for receiving fluid under pressure from the first pressure source means. The distributor valve means including first distributor means for sequentially connecting the pressurized fluid to a particular one of the output ports in timed sequence with the operation of the timing valve means and with the combustion process within the engine. The distributor valve means further including second distributor means for sequentially connecting the particular one of the output ports to the metering valve means for a determinable length of time prior to the time the particular one of the output ports is connected to the first pressure.